Based on your description, I agree you probably need new shifter bushings. Since your car is an 89 G50 (assuming Carrera 3.2) you do not have the coupler bushing shown so far which are for an earlier cars.
G50 coupling
Here are a couple of good shifter rebuild threads and TSBs on the shifter rattle:
Is a chattering sound normal starting out in 1st gear? '88 Carrera
G-50 shift tower bushings
G50 Rattle
Parts list that I used.
999-701-969-40 O-ring for gearshift lever/head shift rod (This is for shifter rattles.)
950-424-224-03 Shift sleeve/friction ring
911-424-139-01 Shift/ball socket
999-701-012-50 O-ring
999-701-923-40 O-ring
For lubricant of the O-rings and movable parts, I used plumber's grease since it has less of a chance of damaging the O-rings and plastics used in the shifter.
Harold
87 Carrera Coupe